Transcript configurations

Wireless Application Programming
with Java
School of Technology of Setubal
Setubal, Portugal
April 9, 2002
Qusay H. Mahmoud
School of Computing Science
Simon Fraser University, Burnaby, B.C., Canada
[email protected]
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1
You will learn:
What is the J2ME platform?
How does it differ from J2SE?
KVM (Kilo Virtual Machine)
Configurations and Profiles
CLDC and MIDP
CDC, Foundation, Personal, RMI
How to get started developing wireless
applications using the J2ME platform
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Outline
Web Content for Mobile Devices
WAP Programming Model
J2ME Platform
KVM (Kilo Virtual Machine)
Configurations and Profiles
CLDC (Connected Limited Device Configuration)
MIDP (Mobile Information Device Profile)
Examples
Availability and Resources
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Web Content for Mobile
Devices
Markup languages to deliver Web content to
device browsers:
HDML
Phone.com (now Openwave)
Compact HTML (cHTML)
NTT DoCoMo’s i-mode network
WAP Forum’s WML
An emerging standard for content delivered to mobile
devices
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WAP Network Structure
The WAP Gateway plays an important role
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WAP Programming Model
Similar to the Web programming model with
extensions for the wireless environment
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WML Example
<?xml version="1.0"?>
<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML
1.1//EN" "http://www.wapforum.org/DTD/wml_1.1.xml">
<wml>
<card id="MyFirstCard" title="First Card">
<p align="center">
My First WML Example
</p>
</card>
</wml>
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Transcoding Proxies
Transcoding proxies are becoming more
capable and widely used
HTML, cHTML, and WML are converging
towards XHTML
XHTML is the re-writing of HTML as an XMLbased markup language
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Java 2 Platform
Virtual Machines and horizontal and vertical
APIs specified in configurations and Profiles
Source: j2me white paper
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Configurations
A configuration defines the minimum APIs
and VM capabilities for a family of devices:
Similar requirements of memory size and
processing capabilities
The minimum APIs that an application
developer can expect to be available on
implementing devices
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Configurations
May not contain any optional features
Defined through the Java Community Process
(JCP)
http://java.sun.com/jcp (www.jcp.org)
Subject to compatibility tests
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Profiles
A profile is a collection of APIs that
supplement a configuration to provide
capabilities for a specific vertical market
Defined through Java Community Process
initiative (www.jcp.org)
Subject to compatibility tests
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How do they fit together?
Profiles are built on top of configurations
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CLDC
Targeted at devices with:
160 to 512 KB of total memory available for
Java technology
Limited power (e.g. battery)
Limited connectivity to a network (wireless)
Constrained User Interface (small screen)
It is available for free download
Reference implementation built using KVM
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MIDP
Targets mobile two-way communication
devices implementing the CLDC
It addresses:
Display toolkit (user input)
Persistent data storage
HTTP based networking using CLDC generic
connection framework
Available for free download
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KVM
Stands for Kilo Virtual Machine
Originated from a research project called
Spotless at Sun Research Labs
Implements the classes defined in the CLDC
specification + some additional UI classes
Note: the UI classes are not part of the
CLDC and can be removed at any time
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KVM…
A complete runtime environment for small
devices
Built from the ground up in C
Small footprint (40 – 80 KB)
Class file verification takes place off-device
Supports multi-threading
Supports garbage collection
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KVM Security
VM level security
Off-device pre-verification
Small in-device verification
Application level security
No Security Manager
Sandbox security model:
Applications run in a closed environment
Applications can call classes supported by the device
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KVM
It runs on Solaris, Win32, and PalmOS
MIDP4Palm (java.sun.com/products/midp4palm)
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Wireless Device Stack
MIDle
t
Other
Profiles
MIDP
Train
Schedule
UI
HTTP
CLDC APIs
KVM
No floats
Host OS
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CLDC Internals
The CLDC specification specifies VM features
required by a CLDC implementation
Specifies requirements and APIs for
Input/Output
Networking
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Beyond the CLDC scope
Profiles implemented on top of CLDC specify
APIs for:
User Interface support
Event handling
Persistent support
High-level application model
An example profile is the Mobile Information
Device Profile (MIDP)
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Language & VM
Compatibility
Goal:
Full java language and VM specification
compatibility
Language-level exception:
No floating point support in CLDC 1.0
No hardware floating point support
Manufacturers and developers can include their own
floating point
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CLDC vs. J2SE JVM
Limitations in CLDC supporting JVM:
No floating point support
No finalization
Limited error handling
No Java Native Interface (JNI)
No support for reflection
No thread groups or daemon threads
No weak references
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CLDC APIs
Classes inherited from J2SE v1.3 are in
packages:
java.lang
java.io
java.util
New classes introduced by the CLDC are in
package:
javax.microedition
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CLDC Libraries: java.lang.*
Boolean
Byte
Character
Class
Integer
Long
Math
Object
Runnable
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Runtime
Short
String
StringBuffer
System
Thread
Throwable
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CLDC Libraries: java.io.*
ByteArrayInputStream
ByteArrayOutputStream
DataInput
DataOutput
DataInputStream
DataOutputStream
InputStream
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OutputStream
InputStreamReader
OutputStreamWriter
PrintStream
Reader
Writer
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CLDC Libraries: java.util.*
Calendar
Date
Enumeration
Hashtable
Random
Stack
TimeZone
Vector
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MIDP internals
 Goal:
MIDP implementation must fit in small footprint
(128KB ROM)
Must run with limited heap size (32-200KB RAM)
To be implemented by device manufacturers,
operators, or developers
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MIDlets
A MIDlet consists of a class that extends the
MIDlet class and other classes as needed
To handle events it must implement the
CommandListener interface
public class MyMIDlet extends MIDlet implements
CommandListener{
}
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MIDP Application Lifecycle
MIDlets move from state to state in the lifecycle:
Start: acquire resources and start executing
Pause: release resources and wait
Destroyed: release all resources and end all activities
Paused
startApp
pauseApp
Active
destroyApp
destroyApp
Destroyed
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MIDlet Packaging
Two or mode MIDlets form a MIDlet suite
One or more MIDlets may be packaged in a
single JAR file that includes:
A manifest describing the contents
Java classes for the MIDlet(s)
Resource file(s) used by the MIDlet(s)
Each jar file is accompanied by a Java
Application Descriptor (JAD) file
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MIDlet Packaging
Java Application Descriptor (JAD) file
provides info:
Configuration properties
Pre-download properties
Size, version, storage requirements
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Example MIDlet
import javax.microedition.midlet.MIDlet;
import javax.microedition.lcdui.*;
public class FirstMIDlet extends MIDlet {
Display display = null;
TextBox tb = null;
public FirstMIDlet() {
display = Display.getDisplay(this);
}
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Example MIDlet …
public void startApp() {
tb = new TextBox("FirstMIDlet", "Welcome to
MIDP Programming", 40, 0);
display.setCurrent(tb);
}
public void pauseApp() { }
public void destroyApp(boolean unconditional) { }
}
}
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Example MIDlet…




Compile (javac)
Preverify (off device preverification)
Create a JAR file: first.jar
Create a JAD file: first.jad
 MIDlet-Name: MyFirst
 MIDlet-Version: 1.0.0
 MIDlet-Vendor: Sun Microsystems, Inc.
 MIDlet-Description: My First MIDlet
 MIDlet-Info-URL: http://java.sun.com/j2me/
 MIDlet-Jar-URL: first.jar
 MIDlet-Jar-Size: 1063
 MicroEdition-Profile: MIDP-1.0
 MicroEdition-Configuration: CLDC-1.0
 MIDlet-1: MyFirst,, FirstMIDlet
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Example MIDlet: Testing
midp –descriptor first.jad
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MIDlet Example: Deploy
To deploy a MIDlet on a web server, you
need to add a new MIME type:
text/vnd.sun.j2me.app-descriptor jad
Use the following command to run:
midp -transient http://hostname/path/first.jad
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Simplifying the
Development Effort
Sun’s Wireless Toolkit
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MIDP APIs
The MIDP specifies APIs for:
User Interface
Networking (based on CLDC)
Persistent Storage
Timers
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MIDP User Interface
Not a subset of AWT or Swing because:
AWT is designed for desktop computers
Assumes certain user interaction models
(pointing device such as a mouse)
Window management (resizing overlapping
windows). This is impractical for cell phones
Consists of high-level and low-level APIs
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MIDP UI APIs
High-level API
Applications should be runnable and usable in all
MIDP devices
No direct access to native device features
Low-level API
Provide access to native drawing primitives,
device key events, native input devices
Allows developers to choose to compromise
portability for user experience
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MIDP UI Programming
Model
The central abstraction is a screen
Only one screen may be visible
at a time
Three types of screens:
Predefined screens with complex UI components
(List, TextBox)
Generic screens (Form where you can add text,
images, etc)
Screens used with low-level API (Canvas)
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MIDP UI and Display
The Display class is the display manager
It is instantiated for each active MIDlet
Provides methods to retrieve information
about the device’s display capabilities
A screen is made visible by calling:
Display’s setCurrent(screen);
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MIDP UI Classes
javax.microedition.lcdui classes:
Alert, AlertType, Canvas, ChoiceGroup,
Command, DateField, Display, Displayable, Font,
Form, Gauge, Graphics, Image, ImageItem,
Item, List, Screen, StringItem, TextBox,
TextField, Ticker
javax.microedition.lcdui interfaces:
Choice, CommandListener, ItemStateListener
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MIDP UI Class Diagram
Major classes and interfaces:
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High-Level API Examples
List:
Display display = Display.getDisplay(this);
List menu = new List(“Method of payment”, Choice.EXCLUSIVE);
menu.append(“Visa”);
menu.append(“MasterCard”);
menu.append(“Amex”);
display.setCurrent(menu);
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High-Level API Examples…
Form (Date/Time info):
DateField date = new DateField(“Today’s
date”, DateField.TIME);
Form form = new Form(“Date Info”);
form.append(date);
display.setCurrent(form);
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High-Level Examples…
Form (Sign in screen):
Display display = Display.getDisplay(this);
TextField userName = new TextField(“LoginID:”, “”, 10,
TextField.ANY);
TextField password = new TextField(“Password:”, “”, 10,
TextField.PASSWORD);
Form form = new Form(“Sign in”);
form.append(userName);
form.append(password);
display.setCurrent(form);
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Low-level Example
Canvas:
public class MyCanvas extends Canvas {
public void paint(Graphics g) {
g.setColor(255, 0, 0);
g.fillRect(0, 0, getWidth(), getHeight());
g.setColor(255, 255, 255);
g.drawString("Hello World!", 0, 0, g.TOP | g.LEFT);
}
}
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Low-level Example…
Instantiate and display MyCanvas
public class MyMidlet extends MIDlet {
public MyMidlet() { // constructor
}
public void startApp() {
Canvas canvas = new MyCanvas();
Display display = Display.getDisplay(this);
display.setCurrent(canvas);
}
// pauseApp() and destroyApp()
}
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Input Handling
High-Level API input is handled using
abstract commands
No direct access to soft buttons
Commands are mapped to appropriate soft
buttons or menu items
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Input Handling: Example
TextBox screen with commands:
Display display = Display.getDisplay(this);
TextBox tb = new TextBox(“MIDP”, “Welcome to MIDP
Programming”, 40, TextField.ANY);
Command exit = new Command(“Exit”, Command.SCREEN, 1);
Command info = new Command(“Info”, Command.SCREEN, 2);
Command buy = new Command(“Buy”, Command.SCREEN, 2);
tb.addCommand(exit);
tb.addComment(info);
tb.addCommand(buy);
display.setCurrent(tb);
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Event Handling: High-level
High-level Events:
Based on a listener model
Screen objects can have listeners for commands
For an object to be a listener, it must implement
the CommandListener interface
This interface has one method:
commandAction
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Event Handling: Example
MIDlet implements CommandListener
public class MyMIDlet extends MIDlet implements
CommandListener {
Command exitCommand = new Command(…);
// other stmts
public void commandAction(Command c, Displayable s) {
if (c == exitCommand) {
destroyApp(false);
notifyDestroyed();
}
}
}
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Event Handling: Example
Handling List events:
public void commandAction(Command c, Displayable d) {
if (c == exitCommand) { ..
} else {
List down = (List)display.getCurrent();
switch(down.getSelectedIndex()) {
case 0: testTextBox();break;
case 1: testList();break;
case 2: testAlert();break;
case 3: testDate();break;
case 4: testForm();break;
}
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Event Handling: Low-level
Low-level Events:
Low-level API gives developers access to key
press events
Key events are reported with respect to key
codes
MIDP defines key codes: KEY_NUM0 ..
KEY_NUM9, KEY_STAR, KEY_POUND
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Handling Events: example
Low-level events
protected void keyPressed(int keyCode) {
if (keyCode > 0) {
System.out.println("keyPressed " +((char)keyCode));
} else {
System.out.println("keyPressed action “
+getGameAction(keyCode));
}
}
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MIDP UI Design Principles
Make the UI simple and easy to use
Use the high-level API (portability)
If you need to use low-level API, keep to the
platform-independent part
MIDlets should not depend on any specific
screen size
Entering data is tedious, so provide a list of
choices to select from
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Networking
J2SE and J2EE networking APIs are not
suitable for handheld devices
Require several megabytes of memory to run
Device manufacturers who work with circuitswitched networks require TCP support
Device manufacturers who work with packetswitched networks require UDP support
Other devices have specific mechanisms for
communications
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CLDC Generic Connections
A set of related abstractions at the
programming level
No abstractions for different forms of
communications
All connections are created using the
Connector.open()
If successful, it returns an object that
implements one of the generic connection
interfaces
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Connection Interfaces
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Example Connections
HTTP:
Connector.open(“http://www.host.com”);
Socket:
Connector.open(“socket://host.com:80”);
Datagram:
Connector.open(“datagram://address:port”);
File: Connector.open(“file:/myfile.txt”);
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Advantages of CLDC
Generic Connections
Isolate the differences between the setup of
one protocol and another
Most of the application code remains the
same regardless of the protocol you use
Note: CLDC itself does not provide any
protocol implementation
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MIDP Connectivity
It provides support for HTTP
(HttpConnection)
Why? HTTP can be implemented using IP
protocols or non-IP protocols
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HttpConnection
Part of the javax.microedition.io
Defines the necessary methods and
constants for an HTTP connection
HttpConnection c = (HttpConnection)
Connector.open(“http://quotes.yahoo.com”);
C.setRequestMethod(HttpConnection.POST);
C.setRequestProperty(“Content-Language”, “en-CA”);
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Invoking Remote
Applications
A MIDlet may invoke remote applications:
Fetching a page
Invoking a CGI script (GET or POST method)
Invoking a Servlet
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Example: Invoke a CGI
Script
GET Method:
String url = “http://host/cgi-bin/getgrade?idnum=182061”;
c = (HttpConnection) Connector.open(url);
c.setRequestMethod(HttpConnection.GET);
// set some request properties: c.setRequestPropert(“ “, “ “);
is = c.openDataInputStream();
while((ch = is.read()) != -1) {
b.append((char)ch);
}
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Example…
If you want to send data to a remote
application:
String s = “stuffToSend”;
byte postmsg[] = s.getBytes();
for(int i=0;i<postmsg.length;i++) {
os.writeBytes(postmsg[i]);
}
// OR
os.write(s.getBytes());
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Servlet as a Mediator
Devices with no IP stack may access and use ‘net
services through a servlet
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Databases
A persistent storage: a place to store the
state of objects
Facilities provided in J2SE and J2EE are not
suitable for handheld devices
MIDP provides a record-oriented database
mechanism to persistently store data and
retrieve it later
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MIDP’s RMS
Lightweight record-oriented database
Device independent API
Unique recordID for each record within the store
A record is an array of bytes
Shared within MIDlet suite
Support for enumeration, sorting, and filtering
javax.microedition.rms
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MIDP RMS Methods
Record Store
openRecordStore, closeRecordStore,
listRecordStore, deleteRecordStore,
getRecordSize, getNumRecords
Record Data
addRecord, deleteRecord, getRecord, setRecord,
getRecordSize
Record Selection
RecordEnumeration, RecordFilter,
RecordComparator
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RMS: Record Stores
To open a record store:
RecordStore db =
RecordStore.openRecordStore(“myDB”, true);
To close a record store:
db.closeRecordStore();
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Create/Add a new record
To create a new record:
ByteArrayOutputStream baos = new
ByteArrayOutputStream()
DataOutputStream dos = new
DataOutputStream(baos);
dos.writeUTF(record);
Byte b[] = baos.toByteArray();
db.addRecord(b, 0, b.length);
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Building a Stock Database
See appendix for source code:
Stock.java
StockDB.java
QuotesMIDlet.java
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StockQuotes MIDlet
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MIDP Timers
Handle queuing and delivery
Timer task:
Multiple tasks per timer
Periodic
Fixed interval
One-time execution
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Tasks
To define a task, create a subclass of
TimerTask:
import java.util.*;
public class MyTask extends TimerTask {
public void run() {
System.out.println(“Run Task”);
}
}
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Tasks…
Schedule it for execution by creating a
Timer object and invoking schedule()
Timer timer = new Timer();
TimerTask task = new MyTask();
// wait five seconds before executing
timer.schedule(task, 5000);
// wait two seconds before executing then
// execute every five seconds
timer.schedule(task, 2000, 5000);
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MIDP Next Generation
MIDP NG will:
Maintain backward compatibility with MIDP 1.0
Continue focus on wireless phones
Maintain small footprint (limit API growth)
Fine tune MIDP 1.0 APIs
Enable mobile commerce
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MIDP Next Generation
Areas to investigate:
HTTPS and secure networking (SSL)
Network connectivity via sockets and datagrams
Formal inclusion of Over The Air Provisioning
Inclusion of a small XML Parser
Sound API
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MIDP for Palm OS >= 3.5
A J2ME application runtime environment
based on CLDC 1.0 and MIDP 1.0
It is targeted at handheld devices (such as
Palm Pilot, Handspring Visor) running Palm
OS 3.5 or higher.
Java Manager: MIDP.PRC
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MIDP for Palm OS
To install:
Place palm device in the craddle
Use Palm Desktop Software to install MIDP.PRC
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MIDP for Palm OS
Comes with a PRC converter tool
C:\midp4palm\java –jar Converter.jar
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MIDP for Palm OS
Install GUI.PRC
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MIDP for Palm OS
To have more control, use command line
tool:
Converting a single MIDlet JAR to PRC file
java –jar MakeMIDPApp.jar –nobeam –o
Stocks.prc –JARtoPRC StockQuotes.jar
StockMIDlet
Converting a MIDlet suite to PRC file
java –jar MakeMIDPApp.jar –jad MySuite.jad –o
MySuite.prc –JARtoPRC MySuite.jar MySuite
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MIDP for Palm OS
Networking and Databases
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Other Configurations/Profiles
PDA Profile (CLDC-based)
Connected Device Configuration (CDC)
CVM
Supports full Java library
Foundation Profile
Personal Profile
RMI Profile
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PDA Profile
www.jcp.org/jsr/detail/75.jsp
Based on the CLDC 1.0
Will provide user interface and data storage
APIs for handheld devices
The UI API is expected to be a subset of the
AWT
No reference implementation yet
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CDC/Foundation
CDC targets the next generation of wireless,
handheld consumer devices
The Foundation Profile is meant to serve as a
foundation for other profiles
It extends the CDC by adding most of the missing
J2SE core libraries, except those related to UI
APIs for beans, rmi, sql are not part of
CDC/Foundation
Reference Implementations are available for Linux
and VxWorks
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CLDC vs. CDC
CLDC implements a
subset of Java features
and APIs
KVM
For limited devices
16 or 32-bit processors
Targets devices with
160-512 KB of memory
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CDC is a full Java
implementation
CVM
For more powerful
devices
32-bit processors
Targets devices with at
least 2 MB of memory
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Personal Profile
PersonalJava is being redefined as the
Personal Profile
It extends the Foundation Profile
Provides GUI capable of running Java web
applets
Backward compatible with 1.1 and 1.2
PersonalJava applications
No reference implementation yet
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RMI Profile
Extends the CDC and Foundation to provide
Remote Method Invocation for devices
Therefore, it is meant to be used with the
CDC/Foundation and not CLDC/MIDP
Requires TCP/IP network connectivity
Compatible with J2SE RMI API 1.2.x or
higher
No reference implementation yet
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Availability and Resources
Sun’s CLDC implementation supports development
using Solaris, Win32, PalmOS
NTT DoCoMo started Java-based cell phone service
in January/01
Motorola announced a Java-enabled GSM phone
(Accompli A008).
Motorola & Nextel (i50sx, i85s)
Nokia, Ericsson, and others
support J2ME
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J2ME SDKs
Sun’s Wireless Toolkit: java.sun.com/j2mewtoolkit
Motorola’s J2ME implementation:
www.motorola.com/java
RIM’s BlackBerry JDE:
developers.rim.net/handhelds
Metrowerks CodeWarrior for Java:
www.metrowerks.com/desktop/java
Zucotto’ WHITEborad SDK
www.zucotto.com
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J2ME Resources
J2ME:
http://java.sun.com/j2me
CLDC and KVM:
http://java.sun.com/products/cldc
MIDP:
http://java.sun.com/products/midp
Wireless Toolkit:
http://java.sun.com/products/j2mewtoolkit
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Additional Resources
KVM Interest Archive:
archives.java.sun.com/archives/kvm-interst.html
Device Programming Forum @ ITWorld.com
forums.itworld.com
J2ME Archive:
www.billday.com/j2me
WirelessDevNet Developer Portal:
www.wirelessdevnet.com
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Thank you
Q&A
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Copyright Info
©Copyright 2001 javacourses.com
All rights reserved.
Java™ and J2ME ™ are registered trademarks of
Sun Microsystems, Inc.
All trademarked product and company names are
the property of their respective trademark
holders.
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Speaker Bio
Qusay H. Mahmoud is a faculty member at the
School of Computing Science at Simon Fraser
University, Canada. Previously, he was a contractor
for Sun Microsystems. He has published dozens of
articles on the Java programming language,
including the MIDP and Palm programming articles
for Sun’s Java Developer Connection. Qusay is the
author of Distributed Programming with Java
(Manning Publications Co., 1999) and the upcoming
Wireless Java from O’Reilly.
http://www.cs.sfu.ca/~qmahmoud
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